Alanylglutamine, with alias N-(2)-L-alanyl-L-glutamine, has the English name L-alanyl-L-glutamine, and the chemical name N-(2)-L-alanyl-L-glutamine. Its molecular formula is C9H15N3O4 with a molecular weight of 217.22. The structure of alanylglutamine is as follows:

Alanylglutamine was first developed and manufactured by Germany's Fresenius AG, and imported into China in 1999. As a parenteral nutrition drug, alanylglutamine can be used to improve patients' cellular immune function, to effectively reduce the risk of infection in critically ill patients, to play an important role especially in the treatment and recovery of severe infections, malignant cancers and other serious injuries, and to shorten the total time length of patient hospitalization. Clinical studies have shown that Gln has good therapeutic effects towards severe metabolic disorders (such as burns/trauma/major surgery, acute and chronic infections, bone marrow transplantation, and multiple organ dysfunction syndrome), bowel dysfunction (such as short bowel syndrome, colitis and chemotherapy induced mucosal damage), and immune deficiency syndrome (such as AIDS, critical illness or bone marrow transplantation associated immune dysfunction). Alanylglutamine can effectively maintain the total number of lymphocytes in the blood circulation, and relieve surgery and chemotherapy-induced immunosuppression, which may be related to the adequate breathing fuel provided to lymphocytes by the Ala-Gln. Alanylglutamine is an very effective parenteral nutrition drug. It can reduce body proteolysis of the gastrointestinal cancer patients after surgery and chemotherapy, effectively improve the nitrogen balance and maintain the number of lymphocytes in the blood circulation, therefore improve patients' nutritional conditions and enhance body tolerance to surgery and chemotherapy.
A number of domestic and foreign references of patents and journals have disclosed processes for synthesizing alanylglutamine. For example:
European Patent EPNO311.057 uses benzyloxycarbonylalanine (Z-ALa) to generate an activated ester in the presence of dicyclohexyl carbodiimide (DCC), condensation with glutamine (Gln) to synthesize a dipeptide, and then deprotection by catalytic hydrogenation to provide alanylglutamine. This method has relatively lengthy steps and requires hydrogenation to remove the protecting group.
In European Patent 595345 (EP595345), water immiscible organic solvents (generally toluene, chloroform and methylene chloride) are used in the reaction between optically pure α-halopropionyl halides and glutamine under low temperature and pH 10 conditions to provide optically pure α-halopropionyl glutamine, which is aminated in aqueous ammonia to provide alanylglutamine. The disadvantage of this method is that optically pure halopropionyl halides are hard to acquire and expensive. Additionally, in the above method, only one of the two diastereomeric isomers: L-alanyl-L-glutamine and D-alanyl-L-glutamine can be obtained in each preparation, which limits the promotion of its applications.
Chinese Patent CN1392156 discloses a process for preparing alanylglutamine, wherein N-protected amino acid reacts with triphenylphosphine, hexachloroethane in an organic solvent to form an active ester; the active ester reacts with glutamine in a mixed aqueous solution of an inorganic base and an organic solvent, then acidification is carried out with an inorganic acid followed by removal of the N-terminal protecting group to provide alanylglutamine. But the reaction generates main product alanylglutamine dipeptide along with byproduct triphenylphosphine oxide.
Chinese Patent CN1786019A discloses a process for preparing alanylglutamine, including the steps wherein esterified L-lactic acid reacts with thionyl chloride in the presence of a catalyst to give 2-chloropropionate; 2-chloropropionate is hydrolyzed with basic solution to give 2-chloropropionic acid; 2-chloropropionic acid reacts with a chlorinating reagent to give 2-chloropropionic chloride; 2-chloropropionic chloride reacts with L-glutamine to provide N-(2-chloro)-propionyl-glutamine; N-(2-chloro)-propionyl-glutamine reacts with aqueous ammonia to generate alanylglutamine dipeptide product. However, in the industrial production processes applying this synthetic method, due to the presence of impurities such as ammonium chloride in the reaction solution, crystallization is needed to remove salts. Currently conventional methods for desalination in the alanylglutamine production processes involve desalting by crystallization using alcohols (e.g. methanol, ethanol, isopropanol etc.) and water.
Therefore, a simple method for preparation and purification of alanyl-L-glutamine is still needed to provide alanylglutamine compound with high purity.